Colt AR15, legal with a Bayonet Mount, Flash Suppressor and a Collapsible Stock and can have a magazine with a high capacity load of more than 30 rounds. Photograph: Thomas Cooper/Getty Images

How many AR15 rifles are there in the US today?

US gun sales, ownership and production statistics are often difficult to get hold of - as you can tell from our look at gun sales today.

The weapon that Adam Lanza is suspected of relying on most heavily as he carried out the Newtown shootings is the AR-15 style rifle. It is similar to the M-16 military rifle used in Vietnam. Police said that James Holmes, who is suspected of carrying out a massacre in a cinema in Aurora, Colorado in July, used an AR-15 rifle. Assault weapons were banned in 1994 but the ban expired in 2004 and has not been reinstated. It was first made by ArmaLite, but is now made by various manufacturers in the United States, predominantly Smith & Wesson, Bushmaster, Armalite, Olympic and others.

We don't know how many have been sold, so we have to estimate how many are manufactured each year. A number of manufacturers now predominantly make AR15-style rifles - so if we can work out how many rifles each makes each year and how many are exported, we can get close to a final number.